Protein chainmail variants in dsDNA viruses

Area of Science:

• Structural biology
• Virology
• Biophysics

Background:

• Biological chainmail, exemplified by bacteriophage HK97, involves concatenated protein rings forming highly stable viral capsids.
• The HK97-like fold is a conserved protein structure crucial for capsid stability and dsDNA genome encapsidation.
• Cryo-electron microscopy (cryoEM) has enabled near-atomic resolution studies of complex viral structures.

Purpose of the Study:

• To explore diverse strategies employed by double-stranded DNA (dsDNA) viruses for constructing stable capsids.
• To analyze the structural variations and auxiliary protein roles in viral chainmail formation.
• To understand the evolutionary emergence of dsDNA viruses and inform bioengineering applications.

Main Methods:

• Analysis of near-atomic resolution structures obtained through cryo-electron microscopy (cryoEM).
• Comparative structural analysis of various dsDNA viruses, including bacteriophages and herpesviruses.
• Examination of protein fold topologies and auxiliary protein interactions.

Main Results:

• Identified three main strategies for constructing viral capsids beyond the basic HK97 model: insertional domains, auxiliary jellyroll protein dimers, and auxiliary protein trimers.
• Demonstrated that these strategies enhance the stability of non-covalent chainmail structures.
• Revealed that complex viruses like herpesviruses utilize a combination of these strategies for hierarchical organization.

Conclusions:

• The HK97-like fold and its variations are fundamental to dsDNA virus capsid architecture.
• Diverse strategies involving auxiliary proteins have evolved to stabilize viral capsids.
• Understanding these viral structures offers insights into viral evolution and potential bioengineering applications.